Fig. 4

cntn2 mutants show MLF defasciculation but lacks nucMLF defects seen in morphants.

Panels A-D show ventral views of the midbrain with anterior to the left. (A–D) Confocal projections of Tg(pitx2c:gfp) embryos labeled with anti-GFP antibody at 24 hpf. Panels F–I show ventral views of the midbrain and anterior hindbrain region with anterior to the left. (A) In a control MO-injected embryo, the nucMLF is found as bilateral groups of tightly clustered cells (delineated by dashed outline). Their axons form tight fascicles (arrow) immediately posterior to the neuron clusters. (B) In a cntn2 MO-injected embryo, the nucMLF neurons are loosely packed, and their axons are defasciculated. (C, D) The nucMLF neurons and axons converge normally in zygotic (Zcntn2−/−) and maternal-zygotic (MZcntn2−/−) mutants. (E) Quantification of nucMLF defects. Number in parenthesis denotes number of embryos. Data are from 2 to 4 experiments. (FI) Zn-12 antibody labeling of the MLF axons in 24 hpf embryos. MLF axons in a cntn2+/+ form a tight fascicle (F); however, MLF axons are defasciculated (arrowheads) in MZcntn2−/− embryos (G-I). Black dotted line in F shows the cut-off point (for scoring) where the trigeminal sensory axons enter the hindbrain in r2. (J) Quantification of MLF defasciculation defects. Number in parenthesis denotes number of embryos. Data are from 2 experiments. Scale bar in D, 50 μm for A-D; Scale bar in F, 50 μm for FI.